The field of the present invention is transmissions having a reverse mechanism. In conventional transmissions having a reverse mechanism for use in motorcycles, saddle type three-wheeled vehicles, etc., a forward shift drum rotated by a first operating element and a reverse shift drum rotated by a second operating element are separately supported within the transmission. Upon rotation of each of these forward and reverse shift drums, shift forks engage in lead grooves in the outer peripheral surface of the drums, so that forward and reverse gears are brought into driving engagement with a drive shaft via shifters integrally mounted to the shift forks.
However, in such conventional transmissions, the reverse mechanism generally includes a lock mechanism to prevent the reverse gear from accidentally being engaged to the drive shaft, when a forward gear is driven. This lock mechanism results in an increase in size, weight, and complexity of the transmission. In addition, the fact that the two shift drums are separately supported within the transmission also requires an increased size of the transmission.